Conversion of 1,4-butanediol to furan compounds on cobalt catalysts in the liquid phase

The transformation of 1,4-butanediol on cobalt catalysts applied to kieselguhr in the liquid phase under periodic and continuous conditions was investigated. When the reaction is carried out under periodic conditions, the principal reaction products are 2,3-dihydrofuran, tetrahydrofuran, and -butyrolactone. An increase in the selectivity of the formation of 2,3-dihydrofuran as the temperature is raised was established. 2,3-Dihydrofuran is obtained in 63–73 mole % yields under optimum conditions. 2,3-Dihydrofuran is converted to tetrahydrofuran when the process is carried out under continuous conditions on a tableted cobalt catalyst.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 448–450, April, 1981.     

Alkyloxycarbonyl group migration in furanosides

A migration of methyloxycarbonyl group from secondary to primary hydroxyl was observed in furanosides (ribosides and xylosides) under usual desilylation conditions using tetrabutylammonium fluoride. The migration was studied further on several alkyloxycarbonyl furanosides under either basic or acidic conditions. As follows from ¹³C labelling experiments and product distribution, the migration in xylosides, proceeds intramolecularly via six-membered cyclic carbonate, whereas in ribosides, the migration is intermolecular. Acidic conditions prevented the migration in ribosides whereas the migration in xylosides was circumvented under neutral conditions.     

预热燃烧模式下半焦NO排放和燃尽特性实验研究

为探究更高预热温度下(1000℃)半焦预热燃烧工艺的降氮潜力,在两段电炉串联组成的沉降炉系统上考察了预热温度(600-1400℃)、燃烧温度(1200-1400℃)和过量空气系数(α=0.6-1.4)对半焦燃烧NO释放和燃尽的影响。结果表明,进一步提高预热温度(1000℃)能够同时降低NO排放和提高燃尽率,并且富燃料工况下,预热温度升高带来的NO降低幅度比贫燃料工况下降低幅度大,预热温度从800℃升高至1400℃时,NO降幅最大可达74%(α=0.6),明显高于贫燃料条件下NO降幅20.6%(α=1.4)。但是,富燃料工况下,预热温度升高带来的飞灰含碳量降幅比贫燃料工况下降低幅度小,贫燃料条件下飞灰含碳量最大降幅为26.8%(α=1.4),高于富燃料条件下降幅15.95%(α=0.6)。对于燃烧温度对半焦燃烧NO释放的影响,发现存在一临界过量空气系数α=1,当过量空气系数高于该临界值时,随燃烧温度提高,NO排放量增加,当过量空气系数低于该临界值时,随燃烧温度的提高,NO排放量减小。     

Use of the ‘characteristic function’ for modelling repeatability precision

The ‘characteristic function’ is a two-parameter function relating precision or uncertainty in analytical results to the concentration of the analyte. In previous papers, in this series, it has been shown to provide a good model of precision measured: (a) under reproducibility conditions and (b) under ‘instrumental’ conditions. The present study shows that it is also a valuable model for precision estimated under repeatability conditions. The study data were large sets of duplicated results obtained for the purposes of quality control on typical test materials in routine analysis. As the analytes exhibited concentration ranges encompassing between one and three orders of magnitude, there was ample scope to demonstrate goodness of fit to the function under different circumstances.     

Phanerochaete mutants with enhanced ligninolytic activity

In addition to lignin, the white rot fungusPhanerochaete chrysosporium has the ability to degrade a wide spectrum of recalcitrant organopollutants in soils and aqueous media. Most of the organic compounds are degraded under ligninolytic conditions with the involvement of the extracellular enzymes, lignin peroxidases, and manganese-dependent peroxidases, which are produced as secondary metabolites triggered by conditions of nutrient starvation (e.g., nitrogen limitation). The fungus and its enzymes can thus provide alternative technologies for bioremediation, biopulping, biobleaching, and other industrial applications. The efficiency and effectiveness of the fungus can be enhanced by increasing production and secretion of the important enzymes in large quantities and as primary metabolites under enriched conditions. One way this can be achieved is through isolation of mutants that are deregulated, or are hyperproducers or supersecretors of key enzymes under enriched conditions. Through UV-light and γ-ray mutagenesis, we have isolated a variety of mutants, some of which produce key enzymes of the ligninolytic system under high-nitrogen growth conditions. One of the mutants, 76UV, produced 272 U of lignin peroxidases enzyme activity/L after 9 d under high nitrogen (although the parent strain does not produce this enzyme under these conditions). The mutant and the parent strains produced up to 54 and 62 U/L, respectively, of the enzyme activity under lownitrogen growth conditions during this period. In some experiments, the mutant showed 281 U/L of enzyme activity under high nitrogen after 17 d.

     

Sorption of radioactive technetium on pyrrhotine

The sorption behavior of technetium on pyrrhotine was studied with batch experiments and diluted sulfuric acid (less than 2.88 mol/l) was used to dissolve the technetium adsorbed on pyrrhotine. A significant sorption of technetium on pyrrhotine was observed under aerobic and anaerobic conditions, and the sorption on the mineral was supposed to be due to the reduction of TcO₄ ^- to insoluble TcO₂ ^.nH₂O. Sorbed technetium on the mineral could be desorbed by diluted sulfuric acid. The maximum desorption ratio under aerobic conditions was much higher than that of under anaerobic conditions, meanwhile, the desorption rates under anaerobic conditions were higher than that of under aerobic conditions in the initial stage of the experiments.     

Fluoride effect on the palladium–phenanthroline catalyzed carbonylation of nitroarenes to carbamates

Fluorides promote the palladium–phenanthroline catalyzed carbonylation of nitroarenes to carbamates. The effect is more evident on the rate of the reaction at short reaction times, but a positive effect on selectivity is also observed under certain conditions. The effect is observed even under conditions under which chloride inhibits the reaction. Tetraethylammonium is a better countercation than sodium. Copyright © 2007 John Wiley & Sons, Ltd.     

Kathodische Reduktion von 2-Azido-2,4-pentadien-1-onen Elektrolytische Untersuchungen an Vinylaziden, 9. Mitt.

Cathodic reduction of 2-azido-2,4-pentadien-1-ones under slightly protic conditions result in aminodienones, whereas under acetylating conditions only the methyl-N,N-diacetylaminoadienoates could be prepared in reasonable yields. The low reduction potential of the N,N-diacetylaminodienones leads to a mixture of by-products. The N,N-diacetylaminodienoates were studied as a model of the reduction of the azidodienes at higher reduction potentials. Dimerisation, reduction of the double-bonds and elimination of the N,N-diacetylamino group are possible reactions. The mechanism of reduction under acetylating conditions is discussed.

     

In vitro degradation of porous poly(l-lactide-co-glycolide)/β-tricalcium phosphate (PLGA/β-TCP) scaffolds under dynamic and static conditions

In vitro degradation of porous poly(l-lactide-co-glycolide)/β-tricalcium phosphate (PLGA/β-TCP) scaffolds was studied by incubating the samples in phosphate buffered saline (PBS) at 37 °C and pH 7.4 under dynamic loading with respect to static conditions for 12 weeks. Under dynamic conditions, acidity of PBS was alleviated by the better solution circulation, and water absorption of the scaffolds increased more than that under static conditions in the first 8 weeks. Changes in mass, height, diameter, relative molecular mass and its distribution also happened more remarkably under dynamic conditions. Moreover, obvious cracks and a larger amount of β-TCP particles were observed on the wall of the scaffolds after degradation for 12 weeks under dynamic loading. Compressive modulus and strength showed an increase from the beginning to the 10th week but were lower after then. Results showed that degradation of PLGA/β-TCP scaffolds under dynamic conditions exhibited a significantly faster rate than that under static conditions.     

Efficient and scalable arylation of bicyclic lactones to form quaternary centers using conventional and microwave radiation

Easily accessible bicyclic lactones were efficiently arylated under modified Hartwig and Buchwald conditions to form quaternary aryl centers with complete cis selectivity. This series is notable in that unreactive substrates, including sterically-demanding ortho-substituted aromatic compounds, enjoyed significant rate acceleration under microwave radiation. Additionally, it was noted that the reactions could be accomplished under standard anaerobic conditions and on multi-gram scale.     

Transformation-Governed Heating Techniques in Thermal Analysis I.

The author gives a detailed survey on thermogravimetric investigations under quasi-isothermal — quasi-isobaric conditions (Q-TG). According to the principle of the technique the heating of the sample is governed by the transformation itself according to the feed-back principle in a way that the transformations should take place at a strictly constant rate, slower by orders of magnitude than in the case of the conventional techniques. Due to this, the transformations take place under ideal conditions, near to physico-chemical requirements.Based on the obtained advantageous results further methods were elaborated, like thermo-dilatometry (Q-TD), evolved gas analysis (Q-EGA) and microdistillation under quasi-isothermal conditions.The second part of the present review deals with DTA and DSC techniques under quasi-isothermal conditions elaborated recentlyThis revised version was published online in November 2005 with corrections to the Cover Date.     

Theoretical Explanation for How SO3H‐Functionalized Ionic Liquids Promote the Conversion of Cellulose to Glucose

While the catalytic transformation of cellulose to glucose by functionalized ionic liquids (ILs) has been achieved successfully under mild conditions, insight into the fundamental molecular mechanism is still lacking. The present work presents the first attempt to address the fundamental reaction chemistry of the catalytic transformation. An enzyme‐like catalytic mechanism of ILs, in which glycosidic bond hydrolysis proceeds through a retaining mechanism and/or an inverting mechanism, is proposed. DFT calculations show that both mechanisms involve moderate barriers (<30 kcal mol^?1), which is consistent with the catalytic performance of the ILs under mild conditions (<100 °C). The “biomimetic” mechanism model proposed herein is expected to be viable for understanding the unique catalytic activity of ILs under mild conditions.     

Selective esterification of the polyphenol resveratrol at the 4′-position

Selective esterification of the polyphenol resveratrol was performed under thermodynamic conditions using NaH and acid anhydrides to directly access 4′-esters. Standard conditions with acetyl chloride and pyridine showed poor selectivity, favoring esterification at the 3-position. The extended 4′-phenolate anion is generated in preference to the 3-phenolate under the new anhydride-sodium hydride-DMSO conditions. Acylation occurs to access the 4′-ester products with modest selectivity and yield with minimal formation of the 3-monoester, 3,5-diester, and triester products.     

VSO4.5H2O: A Mild and Efficient Catalyst for Chemo‐Selective Conversion of Aldehydes to 1,1‐Diacetates

Protection of aliphatic and aromatic aldehydes as 1,1‐diacetates using VSO₄.5H₂O under solvent‐free conditions is carried out. The products are obtained in good to excellent yields. Ketones are not affected under these conditions.     

Oilwell cements: NMR contribution to establish the phase diagram pressure/temperature of the mixture H2O / Ca3SiO5

Cement slurry is always used to support the casing of oilwells. This slurry is pumped down the steel casing of the well and then placed in the annular space between the casing and the surrounding rock. Nowadays wells are becoming deeper and deeper so the setting conditions of the cement paste are crucial. The pressure and temperature limit conditions can reach 1 000 bar and 250 °C at the bottom of the well. Hydration of synthetic tricalcium silicate Ca₃SiO₅ – the main component of oil well cements – was performed at high temperature under high pressure to simulate the oilwell conditions. The objective of the study is the establishment of the phase diagram of the ternary system – SiO₂, CaO, H₂O – according to the parameters: pressure, temperature and Ca/Si ratio. In this study, NMR is largely used to identify and to quantify the synthesized silicate hydrates, with two setting conditions (6 days at 120 °C under 400 bar and 6 days at 200 °C under 600 bar). Mechanical tests were performed to evaluate the compression strength of those silicate hydrates synthesized under such drastic conditions and to verify that they were still efficient binders.     

A simple and efficient one-pot synthesis of 1,4-dihydropyridines using heterogeneous catalyst under solvent-free conditions

One-pot condensation of β-dicarbonyl compounds with aldehydes and ammonium acetate in the presence of HClO₄–SiO₂ at 80 °C under solvent-free conditions with good to excellent yields. The catalyst is easily prepared, stable, reusable and efficiently used under reaction conditions.     

A new InCl3-catalyzed reduction of anthrones and anthraquinones by using aluminum powder in aqueous media

InCl₃-catalyzed reduction of anthrones and anthraquinones was investigated under different conditions. A new synthetic method for anthracenes in aqueous media under mild conditions is described.     

Investigation of m-nitroaniline formation during the Zimmermann reaction

The Zimmermann reaction for the determination of 17-ketosteroids was tested under both room-temperature and steam-distillation reaction conditions. meta-Nitroaniline was isolated from the residue of the steam distillation by ether extraction and thin-layer chromatography. Conclusive identification was by infrared spectroscopy. In contrast, m-nitroaniline was not formed under room-temperature reaction conditions, even when allowed to react for 24 hr. Similar results were also obtained for the reaction between acetone and m-dinitrobenzene under alkaline conditions. In conclusion, the results indicate that m-nitroaniline formation cannot account for the conversion of structure I to structure II under room-temperature reaction conditions as investigated herein.     

An investigation of the bactericidal and fungicidal effects of certain disinfectants by use of a capacity test

The bactericidal and fungicidal effects of five disinfectants and one combination of two disinfectants were tested using a modified Kelsey-Sykes method in which living microorganisms suspended in a sterilized yeast suspension («dirtyå conditions) and in sterile distilled water («cleanå conditions) were added to the disinfectants in three stages. Six bacteria and two fungal organisms were employed as test microbes.Results showed that formaldehyde was virtually inactive at the dilution tested (1/50), whereas phenol and the combination propylene-phenoxetol +benzalkonium chloride were moderately effective, the latter compound being better. Glutaraldehyde was manifestly the most effective of the disinfectants tested, followed by tricresol. At a 1/50 dilution, chloramine proved to have a surprisingly strong fungicidal effect on Candida albicans and Aspergillus fumigatus under «dirtyå conditions, whereas the same fungal organisms proved rather resistant to chloramine under «cleanå conditions. The same was demonstrated–though less markedly—when higher dilutions o chrloramine were used. The search for an explanation is still in progress. At relatively high dilutions, chloramine also proved effective against most of the test bacteria, especially under «cleanå conditions. It is recommended that the yeast suspension of chloramine against fungal strains under «dirtyå conditions.     

Metal‐Free Annulation of Arenes with 2‐Aminopyridine Derivatives: The Methyl Group as a Traceless Non‐Chelating Directing Group

A novel annulation reaction between 2‐aminopyridine derivatives and arenes under metal‐free conditions is described. The presented intermolecular transformation provided straightforward access to the important pyrido[1,2‐a]benzimidazole scaffold under mild reaction conditions. The unprecedented application of the methyl group of methylbenzenes as a traceless, non‐chelating, and highly regioselective directing group is reported.